Chapter 6 Igmp Configuration; Introduction To Igmp; Igmp Version - Huawei Quidway S3900 Series Operation Manual

Operation Manual – Multicast Protocol
Quidway S3900 Series Ethernet Switches-Release 1510

Chapter 6 IGMP Configuration

6.1 Overview

6.1.1 Introduction to IGMP

Internet group management protocol (IGMP) is responsible for the management of IP
multicast members. It is used to establish and maintain membership between IP hosts
and their directly connected neighboring routers.
However, the IGMP feature does not transmit and maintain the membership
information among multicast routers. This task is completed by multicast routing
protocols. All the hosts participating in multicast must support the IGMP feature.
IGMP is divided into two function parts:
Host side: the hosts participating IP multicast can join or exit a multicast group
anywhere and anytime, without being restricted on the total number of group
members.
Router side: through the IGMP protocol, a multicast router checks the network
segment connected with each interface to see whether there are receivers of a
multicast group, namely, group members.
A multicast router need not and cannot save the membership information of all the
hosts. While, a host has to save the information that which multicast groups that it joins
in.
IGMP is asymmetric between the host and the router. The host needs to respond to the
IGMP query packets of the multicast routers, that is, report packet responses as an
IGMP hosts. The multicast router sends IGMP general query packets periodically and
determines whether any host of a specified group joins in its subnet based on the
received response packets. When the router receives IGMP leave packets, it will send
IGMPv2 group-specific query packets to find out whether the specified group still has
any member.

6.1.2 IGMP Version

IGMP has three versions until now, including: IGMP Version 1 defined by RFC1112,
IGMP Version 2 defined by RFC2236 and RFC Version 3. IGMP Version 2 is the most
widely used currently.
Compared with IGMP Version 2, the advantages of IGMP Version 2 are:
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Chapter 6 IGMP Configuration